Carburetor bowl vent

ABSTRACT

The float bowl of a carburetor has an insert mounted in the top portion to reduce fuel vapor emissions, the insert having a mazelike channel formed to lengthen considerably the distance the fuel vapor must travel prior to flow through an internal vent tube to the induction passage, to reduce normally excessive fuel delivery at low rpms resulting from engine pressure pulsation.

I United States Patent 11 1 1111 3,814,392 Boyd et al. June 4, 1974 CARBURETOR BOWL VENT 3,093.124 6/1963 Wentworth [23/136 ,3 3,8 9 9 9 1 1 D. @4261, 7192; 1:11;, .1511; Mlch Dale, Benfleet; 3,460.522 8/1969 Kittler et ul 261/72 R Roy Jones, B1shops Stortford. bo h 3,728,092 4/1973 German, Jr 123/136 of England FOREIGN PATENTS OR APPLlCATlONS [73] Asslgnee: l' Motor Company Dearbom, 769,648 3/1957 Great Britain 261/72 R Mlch- 333,952 5/1960 Great Britain 261/72 R [22] Filed: Sept. 21, 1972 Primary Examiner-Tim R. Miles ['21] PP 291,112 Altamey, Agent, or FirmRobert E. McCollum; Keith L. Zerschling [30] Foreign Application Priority Data Apr. 4. 1972 Great Britain 15272/72 [57] ABSTRACT The float bow] of a carburetor has an insert mounted [52] US. Cl. 261/72 R, 26l/DIG. 67 in the top portion to reduce fuel vapor emissions, the [51] Int. Cl. F02m 5/08 insert having a maze-like channel formed to lengthen [58] Field of Search 26l/DIG. 67, 72 R; considerably the distance the fuel vapor must travel 123/136 prior to flow through an internal vent tube to the induction passage, to reduce normally excessive fuel de- [56] References Cited livery at low rpms resulting from engine pressure pul- UNITED STATES PATENTS satlon- 2,894,736 7/1959 Wentworth 123/136 6 Claims, 3'Drawing Figures PAIENTEDJUN 4 m4- V 3.814.392 sum 1 m2 F'IGHIL 1 CARBURETOR BOWL VENT This invention relates to carburetors for internal combustion engines for motor vehicles and in particular to float bowl vent arrangements in such carburetors.

Current or proposed legislation relating to the emission of fuel vapor from motor vehicles limits the quantity of fuel which may be emitted from the engine during the hot soak period, i.e., after the engine has been turned off. In order to meet the requirements of such legislation, it is necessary in some instances to vent the float bowl of a carburetor internally. When an external bowl vent is replaced with an internal bowl vent, there is frequently an unwanted increase in fuel delivery at wide open throttle and low revolutions per minute. This increase in fuel delivery is believed to be caused by variations in the pressure within the float bowl which result from pulsing or pressure variations transmitted back along the inlet manifold to the carburetor.

According to the invention a carburetor has an internal bowl vent comprising a passage of length substantially greater than the direct distance from the float bowl to the air horn to reduce pressure fluctuations in the float bowl.

We have found that by correctly selecting the length of the passage-the fuel delivery at low revolutions per minute can be reduced approximately to the desired value achieved with an external bowl vent.

The invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 is a fragmentary cross-sectional view of a carburetor air horn and bowl vent embodying the invention,

FIG. 2 is a plan view of the vent passage insert used in the construction of FIG. 1 takenon a plane and viewed in the direction of the arrows 2-2 of FIG. 1; and,

FIG. 3 is a graph showing the variation of fuel flow with changes in engine rpm at full load for the same engine and carburetor using (1 a conventional external vent, (2) a conventional internal vent, and (3) an internal vent embodying the invention.

A carburetor for an internal combustion engine in a motor vehicle includes an air horn portion 11 having the usual induction passage 2 through which air is admitted from an air cleaner to the intake manifold of the engine. Fuel to be inducted into the carburetor in a known manner is supplied to a float bowl l2 and maintained at a constant level, also in a known manner. The vapor space in the float chamber above the fuel level is closed except for a vent connected to thecarburetor air horn comprising a stack tube 13 and an insert having a maze passage 14.

The maze passage 14 is formed by an open sided worm-like channel 15 (FIG. 2) in a plastic insert 16 mounted in a suitable manner not shown in the upper part of the float bowl. The under or open side of the insert is covered by a flat closuremember 17. One end 18 of the mazepassage I4 communicates via a vertical passage with one end of the stack tube 13. The other end 19 of the maze passage 14 opens into the vapor space in the top of the float bowl.

In a specific example illustrated in FIG. 3, the fuel flow was calibrated over a range of different engine speeds at full load or wide open throttle conditions. first with an external bowl vent (curve 1), and then with a conventional internal bowl vent (curve 2). The conventional internal bowl vent would consist merely of a connector like tube 13 in FIG. 1, without the maze 14. The tube in FIG. 3, curve 2 was a stack tube 35 millimeters long and 4 millimeters internal diameter.

As can be seen from FIG. 3, the conventional internal vent produced a hump in the fuel curve between 1,000 and 2,500 revolutions per minute. The practical affect of this hump is that the engine is provided with a mixture that is too rich and its torque is reduced.

Curve 3 shows the affect of adding the maze insert 16 which increased the effective length of the internal vent passage from 35 millimeters to 260 millimeters. The cross-sectional area of the undulating maze passage was equivalent to a diameter of 4 millimeters. It will readily be appreciated from FIG. 3 that the longer vent substantially reduces the hump in curve 2 and brings the fuel flow curve almost back to the levels found with an external bowl vent.

In each engine and carburetor combination, there will bean optimum value for the length of the vent channels which can be found by trial and error. If the vent channel is less or greater than this optimum value by a significant amount the fuel flow will be too great in the critical 1,000 to 2,500 revolutions per minute.

Instead of using a plastic insert, the maze passage may alternatively be formed integrally with the upper body of the carburetor.

We claim:

1. An internal vent for the float bowl of a carburetor having an induction passage for the flow of an air/fuel mixture therethrough connected to an air inlet at one end and adapted to be connected to an engine intake manifold at the other end, comprising, i

a passage connecting the vapor space of the fuel bowl to the induction passage at a point adjacent the air inlet portion thereof, the passage being so constructed and arranged as to provide a path for the flow of fuel vapor to be vented of an effective length substantially longer than the actual distance from the float bowl to the induction passage, the passage comprising an insert positioned in the float bowl restricting flow of fuel vapor therefrom to the induction passage by means of a tortuous path.

2. An internal vent for the float bowl of a carburetor having an induction passage for the flow of an air/fuel mixture therethrough connected to an air inlet at one end and adapted to be connected to an engine intake manifold at the other end, comprising,

a passage connecting the vapor space of the fuel bowl to the induction passage at a point adjacent the air inlet portion thereof, the passage being so constructed and arranged as to provide a path for the flow of fuel vapor to be vented of an effective length substantially longer than the actual distance from the floatbowl to the induction passage, the passage comprising a winding channel-like maze open at one end to the float bowl and at its opposite end to the induction passage, including an insert mounted adjacent the top portion of the floatbowl, the insert having a maze-like channel formed on the underside thereof, and means covering the channel except for an opening connected to the float bowl vapor space and a second opening connected to the induction passage.

3. An internal vent for the float bowl of a carburetor having an induction passage for the flow of an air/fuel mixture therethrough connected to an air inlet at one end and adapted to be connected to an engine intake manifold at the other end, comprising,

a vapor vent tube connecting the induction passage to the upper portion of the fuel bowl, the upper portion containing a winding maze-like passage extending along the upper portion in an essentially horizontal plane essentially at right angles to the induction passage for flow of fuel vapor in the same plane, the passage being connected at one end to the tube and at its other end to fuel vapor to provide a path for the flow of fuel vapor to be vented of an effective length substantially longer than the actual distance from the float bowl to the induction passage.

4. An internal vent for the float bowl of a carburetor having an induction passage for the flow of an air/fuel mixture therethrough connected to an air inlet at one end and adapted to be connected to an engine intake manifold at the other end, comprising,

' a passage connecting the vapor space of the fuel bowl to the induction passage at a point adjacent the air inlet portion thereof, the passage being so constructed and arranged as to provide a path for the flow of fuel vapor to be vented of an effective length substantially longer than the actual distance from the float bowl to the induction passage, the passage comprising a winding channel-like maze open at one end to the float bowl and at its opposite end to the induction passage, 'the passage including a tube connecting the induction passage to the top portion of the float bowl, and an insert in the float bowl top portion constituting a closed maze connected at one 'end to the float bowl vapor space and at its other end to the tube.

5. An internal vent as in claim 4, the insert having an undulating channel formed therein having a length substantially longer than the direct distance between the float bowl vapor space and the induction passage.

6. An internal vent as in claim 5, the channel being formed in the lower face of the insert, and a plate mem-' ber covering the channel to close the same except for an opening at one endconnected to the vapor space, and an opening at the opposite end connected through the insert to the opposite side and to the tube. 

1. An internal vent for the float bowl of a carburetor having an induction passage for the flow of an air/fuel mixture therethrough connected to an air inlet at one end and adapted to be connected to an engine intake manifold at the other end, comprising, a passage connecting the vapor space of the fuel bowl to the induction passage at a point adjacent the air inlet portion thereof, the passage being so constructed and arranged as to provide a path for the flow of fuel vapor to be vented of an effective length substantially longer than the actual distance from the float bowl to the induction passage, the passage comprising an insert positioned in the float bowl restricting flow of fuel vapor therefrom to the induction passage by means of a tortuous path.
 2. An internal vent for the float bowl of a carburetor having an induction passage for the flow of an air/fuel mixture therethrough connected to an air inlet at one end and adapted to be connected to an engine intake manifold at the other end, comprising, a passage connecting the vapor space of the fuel bowl to the induction passage at a point adjacent the air inlet portion thereof, the passage being so constructed and arranged as to provide a path for the flow of fuel vapor to be vented of an effective length substantially longer than the actual distance from the float bowl to the induction passage, the passage comprising a winding channel-like maze open at one end to the float bowl and at its opposite end to the induction passage, including an insert mounted adjacent the top portion of the float bowl, the insert having a maze-like channel formed on the underside thereof, and means covering the channel except for an opening connected to the float bowl vapor space and a second opening connected to the induction passage.
 3. An internal vent for the float bowl of a carburetor having an induction passage for the flow of an air/fuel mixture therethrough connected to an air inlet at one end and adapted to be connected to an engine intake manifold at the other end, comprising, a vapor vent tube connecting the induction passage to the upper portion of the fuel bowl, the upper portion containing a winding maze-like passage extending along the upper portion in an essentially horizontal plane essentially at right angles to the induction passage for flow of fuel vapor in the same plane, the passage being connected at one end to the tube and at its other end to fuel vapor to provide a path for the flow of fuel vapor to be vented of an effective length substantially longer than the actual distance from the float bowl to the induction passage.
 4. An internal vent for the float bowl of a carburetor having an induction passage for the flow of an air/fuel mixture therethrough connected to an air inlet at one end and adapted to be connected to an engine intake manifold at the other end, comprising, a passage connecting the vapor space of the fuel bowl to the induction passage at a point adjacent the air inlet portion thereof, the passage being so constructed and arranged as to provide a path for the flow of fuel vapor to be vented of an effective length substantially longer than the actual distance from the float bowl to the induction passage, the passage comprising a winding channel-like maze open at one end to the float bowl and at its opposite end to the induction passage, the passage including a tube connecting the induction passage to the top portion of the float bowl, and an insert in the float bowl top portion constituting a closed maze connected at one end to the float bowl vapor space and at its other end to the tube.
 5. An internal vent as in claim 4, the insert having an undulating channel formed therein having a length substantially longer than the direct distance between the float bowl vapor space and the induction passage.
 6. An internal vent as in claim 5, the channel being formed in the lower face of the insert, and a plate member covering the channel to close the same except for an opening at one end connected to the vapor space, and an opening at the opposite end connected through the insert to the opposite side and to the tube. 